An iontophoresis is a method of ionizing a medicament by passing electric current through the medicament thereby permitting absorption of the medicament in an ionized state through the skin. The method also involves attaching a medicament to one of a cathode or an anode, mounting both electrodes on the skin with a definite interval, and introducing an electric current to the electrodes from an electric current generator by a leading wire is generally employed (see, e.g., Japanese Patent Application (OPI) Nos. 156475/85, 188176/85, 31169/86, etc.). (The term "OPI" as used herein means an "unexamined published application").
In this case, a medicament which is positively ionized is fixed to an anode and a medicament which is negatively ionized is fixed to a cathode. In these electrodes, as the electrode which does not carry a medicament, a conductive gel layer permeated with sodium chloride is usually used. The absorption of a medicament by the iontophoresis is generally better as the electric current and voltage applied are higher. However, when a high electric current of high voltage is passed through the skin for a long period of time, a skin injury such as rubescene, burning, occurs. This sometimes reduces the absorption of medicament through the skin as well and complicates the administration of medicament by iontophoresis. For solving these problems, an iontophoresis method employing a system of passing high frequency pulse electric current was recently proposed (see, Japanese Patent Application (OPI) No. 31169/86).
Now, the absorption extent of medicament by iontophoresis is influenced by a plaster structural assembly containing medicament in addition to the intensity of electric current and the time for passing the electric current. As a conventional plaster structural assembly for iontophoresis, there are known a structural assembly wherein an electrode is covered by absorbent cotton impregnated with medicament, a structural assembly wherein a liquid containing medicament is infused into a tubular cap closely adapted to the skin and an electrode is connected to the cap, and a structural assembly wherein a conductive electrode layer and a medicament-containing conductive gel layer are simply laminated.
However, these plaster structural assemblies have disadvantages in that the absorption of medicament is insufficient and also the absorption decreases with the passage of time. Also, the first two plaster structural assemblies are inconvenient for handling and hence there are problems for practical uses.